Under this grant a rapid non-invasive technique to obtain dimensions and mechanical properties of airways is being investigated. In this technique an acoustic impulse is applied as a barely noticeable input at the mouth in a simple procedure requiring minimum cooperation of the subject. The reflected pressure signal is recorded in time and then analyzed to obtain the airway characteristics. The primary characteristic to be obtained is the cross-sectional area as a function of distance along the airway and the secondary characteristic is the local compliance of the airway. The primary analysis is to be accomplished by a deconvolution procedure while the secondary analysis will require a more complicated inverse method. A pilot experimental study supports the initial theoretical analysis in providing evidence that there is usable and relevant information about the airways of the lung in this reflected signal. The present proposal is to develop this method and test it against direct airway measurements in order to assess its limits of usefulness in vivo. BIBLIOGRAPHIC REFERENCE: Fredberg, J.J., A.C. Jackson and S.V. Dawson. Spark discharge: a new technique for obtaining lung airway response. Medical Instrumentation 9: 64, 1975. (Abstract.)